Among Jews who immigrated to Israel from Libya, Creutzfeldt-Jakob disease (CJD) is 30 to 100 times more common than in any other ethnic group. This focus of CJD offered a unique opportunity to determine how the disease was acquired. A variety of questions were asked of patients and matched controls to elicit differences which might be of etiologic importance. An anthropological approach was used to compare life styles among the groups. Because kuru, a similar slow infection of the central nervous system is believed to be acquired through ingestion of brain, particular attention was paid to diet in the present study. All questions pertained to the period prior to immigration to Israel, because only then did the affected share an environment different from groups with low rates of CJD. The affected did not differ from Libyan controls in place of residence, type of housing, water source, sanitation, health care practices, occupation or education. Tunisian controls differed from Libyans in having higher standards of living and better sanitation. Type of food including consumption of sheep and cattle brain was similar among all subjects but Libyans preferred to prepare brain by grilling while Tunisians preferred simmering. Neither method, however, is likely to destroy the highly resistant transmissible agent of CJD. A high consanguinity rate was found both among Libyans and Tunisians but it was not unusually high for North African Jews. Like Bobowick's et al (1973) study which examined similar variables in cases and controls, no variable was clearly implicated as different in CJD patients compared to matched controls but, both Bobowick et al (1973) and we demonstrated that brain comsumption was common among the affected. Therefore, acquisition of CJD through consumption of contaminated brain remains a possibility.